Thrips: How to Identify Them, Spot the Damage, and Get Rid of Them

What are thrips?

Thrips are tiny, thin insects in the order Thysanoptera that feed by scraping into plant cells and sucking out the contents. Most are 1 to 2 mm (about 1/25 to 1/16 inch) long, shaped like a grain of rice, and yellow, brown or glossy black. The adults have two pairs of narrow wings edged with long hairs, like tiny feathers.

There are more than 6,000 species, and most do no harm at all. Some even eat other pests. A small number feed on houseplants, flowers, vegetables and fruit, and those are the ones people search for. The name is both singular and plural, so one insect is still “a thrips”.

You can see them, but only just. To the naked eye an adult looks like a short dark line or a moving splinter. The young ones look like pale, fast-moving slivers. A phone camera on full zoom or a cheap hand lens shows the shape clearly.

One size figure online is wrong, so it is worth stating plainly. The Missouri Botanical Garden’s indoor page says adults are “about 1/5 inch” long. That is 5 mm, more than twice the size of the common kinds. The University of Maryland Extension gives 2 mm or less, and UC IPM says they are less than 1/20 inch. A few tropical species do reach 14 mm, but you will not meet those on a houseplant.

Thrips damage: the signs on leaves and flowers

Thrips damage shows up as silvery or bleached patches on leaves, often with tiny black specks in them. Each speck is a drop of their droppings, called frass. New leaves may open curled, twisted or scarred, flower buds may fail to open, and petals get pale streaks. The damage is usually easier to see than the insects.

The silver colour has a simple cause. These insects punch into the surface cells and suck them empty, and the University of Maryland notes they do it with odd mouthparts that have only one working jaw. The emptied cells die and turn pale, and many of them together form the silvery patches. Here are the signs, roughly in the order people notice them:

• Silvery or bleached patches on the leaf surface, which can look sunken on thick leaves.
• Black specks like tiny tar dots, inside or beside the pale patches. This is thrips poop.
• Curled, crinkled or stunted new leaves, because they feed in the bud before it opens.
• Streaked or spotted petals and buds that turn brown and drop without opening.
• Rough, scarred skin on fruit such as peppers.

A few insects rarely cause much harm. The University of Maryland says low numbers seldom leave obvious damage, which is why most people only notice once a colony is well established. On a houseplant, check the underside of the leaves, along the main vein, and the spot where each leaf stalk joins the stem.

Thrips or spider mites? Telling the damage apart

This is the most common mix-up, and the fix is different, so check before you spray. Spider mite damage is made of fine, pale dots, and heavy cases bring webbing. Thrips damage is made of silvery streaks and patches, with black specks and no webbing. A quick look at the pest itself settles it.

Look-alikes from the University of Maryland Extension. Sizes for mites, aphids and gnats from our own guides.

If you see webbing and round specks, read our guide to spider mites on houseplants. If the bugs are soft and pear-shaped with sticky leaves below them, our aphid identifier covers them. Small dark flies around the soil are a different pest too: see fungus gnats in potting soil.

How to check a plant for thrips

The easiest test is the white paper shake. Hold a sheet of white paper under a leaf or flower and tap it sharply a few times. Then watch the paper. Specks that start to run, or slim pale slivers that wriggle, are almost always thrips. UC IPM uses the same method, with white paper or cloth.

Next, look closely at the places they hide: the underside of leaves along the veins, inside half-open new leaves, deep in flowers, and where the leaf stalk meets the stem. A phone camera on full zoom works well. After that, put up a sticky card to watch for adults over the coming week.

Blue and yellow cards both catch them. UC IPM suggests blue or bright yellow traps, and the Missouri Botanical Garden suggests light blue cards hung no more than two feet above indoor plants. As a result, the card becomes your scoreboard for the whole treatment.

Still not sure? Take a sharp photo of the insect, not just the damaged leaf, and run it through the free insect identifier. Damage alone can point in two directions, but the insect itself is easy to name from a clear picture.

Thrips larvae, eggs and life cycle

Thrips go from egg to adult in about a month at 60°F (16°C) and in 2 weeks or less at 85°F (29°C), according to the University of Maryland. A female cuts a slit in a leaf, petal or stem and lays her eggs inside it. The young feed for one to two weeks, then rest as non-feeding pupae, usually in the soil, before the adult comes out.

Stage lengths from the Missouri Botanical Garden, the University of Maryland, UF/IFAS and NC State Extension. Warmer rooms make every stage shorter.

Two facts explain why numbers explode. First, the University of Maryland notes that females can lay eggs without mating, so most of the insects on a plant are female. Second, each one lays from a couple of dozen to a couple of hundred eggs. Outdoors, UC IPM counts up to about eight generations a year. Indoors there is no winter break.

People also search for “baby thrips” and “white thrips”. Both are usually the larvae. They look paler and softer than the adults, but they are the same insect. Orange or amber ones can be adults of a lighter species. Maine’s pest program, for example, describes adult greenhouse thrips as yellowish brown to amber with an orange thorax.

Where the pupae hide, and why it matters

UC IPM says the pupae of most species drop to the soil or leaf litter, or lodge in plant crevices. That is why most advice tells you to treat the soil. However, not every kind does it. UF/IFAS says chilli thrips pupae are usually found on the plant, and NC State says banded greenhouse thrips, a common houseplant species, pupate on the leaves, mostly underneath.

For you, this means a soil treatment alone can miss part of the colony. A routine that only drenches the pot lets the leaf-dwelling pupae hatch into new adults. That is one reason the plan below covers the leaves and the soil together.

Types of thrips

Only an expert can name the species, and UC IPM warns that colour alone is not reliable. Even so, the type rarely changes what you do at home. The table lists the kinds you are most likely to meet in the US and the plants they favour, so you know whether your plant is a typical target.

From UC IPM, UF/IFAS (chilli thrips and Thrips parvispinus) and NC State Extension (banded greenhouse thrips).

The aroids that houseplant collectors love are frequent hosts. The University of Maryland lists alocasia, philodendron and anthurium among the indoor plants most often hit, along with orchids, peperomia, ficus, palms, miniature roses and herbs. African violets and spiderworts are especially prone, according to the Missouri Botanical Garden.

Thrips that eat other pests

Some thrips are on your side. UC IPM lists several predatory kinds, including the sixspotted thrips, which has three dark spots on each front wing and feeds in spider mite colonies. Banded-wing thrips and black hunter thrips eat mites and pest thrips too. If you find thrips only among spider mites, look for the spots before you spray.

Are thrips harmful? Do they bite?

Thrips are harmful to plants but not to people. They weaken a plant by emptying its cells, and a few kinds spread plant viruses. They do not feed on blood, Wikipedia’s summary of the research notes, and no human or animal disease is known to spread through them. Now and then, a few kinds give people an itchy nip.

Harm to plants

Most established houseplants survive thrips, even when they look bad. The real losses are flowers that never open, seedlings and young plants, and fruit that ends up scarred. Damaged leaves never turn green again, so the plant looks worse for a while even after the insects are gone.

The bigger risk is in the vegetable garden. UC IPM says western flower thrips spread tomato spotted wilt virus and impatiens necrotic spot virus, which can kill tomatoes, peppers, impatiens and many other plants. A plant virus has no cure, so remove an infected plant to protect the rest.

Do thrips bite people?

Yes, occasionally. A 2005 review in the journal Florida Entomologist recorded three species biting people in Georgia and Florida. The reactions ranged from mild irritation to a rash with intense itching that lasted several days. In Florida, the problem peaked from February to April, when the insects were most plentiful.

They bite while exploring skin on hot days, not to feed. The same study found the Florida species is drawn to white and blue, and people in white or blue clothing appeared to be at greater risk. NC State notes that banded greenhouse thrips can bite too, causing minor itching. Wearing darker colours outside on peak days may help.

A bite cannot be traced back to an insect by looking at it, so do not try to identify the biter from the mark. Our bug bite identification guide explains what the common bites do and do not tell you, and when a bite needs a doctor.

Pets

These insects do not feed on animals. For pets, the real risk is the treatment, not the pest. Keep cats and dogs out of the room while you spray, let the plant dry before they can reach it, and store every product out of reach.

Where do thrips come from?

Indoors, thrips almost always arrive on a new plant, a plant brought in from outdoors, or cut flowers. Adults also drift in through open windows in summer. The Missouri Botanical Garden warns that moving plants indoors in fall can bring insects with them. Once inside, the colony breeds all year, because a heated home has no winter.

Many people only notice them in winter or spring. Indoor air is dry in winter, and the University of Maryland notes that high humidity may discourage them. New growth in spring then gives them fresh, tender leaves. One plant owner on Reddit wrote that they thought their leaves looked rough because of a harsh winter, until they looked closer.

Can thrips infest a house?

Not the house itself. They need living plants to feed and breed, so they do not live in carpets, beds, walls or furniture. The ones you find on a windowsill, on laundry or on your arm in summer have blown in from outside. A colony indoors means a plant is hosting them, so the fix is always on the plants.

If tiny dark specks are moving around the house away from any plant, they may be something else. Our guide to small black bugs in the house sorts the common ones by room and size. Likewise, pale specks on damp soil are more often springtails, covered in our tiny white bugs guide.

How to get rid of thrips

To get rid of thrips, isolate the plant, rinse every leaf with a strong stream of water, cut off the worst leaves and flowers, and refresh the potting mix. Then spray with insecticidal soap or spinosad about once a week, as the label allows, for at least 6 weeks. Repeating is the whole trick, because eggs inside the leaves keep hatching.

UC IPM calls thrips difficult to control and advises combining methods. In other words, no single spray, drench or bug will end it. The order below starts with what costs nothing and ends with the options most homes never need.

1. Isolate, rinse and prune (free)

These three steps cost nothing and remove most of the insects in one go. The University of Maryland suggests rubbing off the young or knocking them off with a strong jet of plain water, spraying both leaf surfaces. Then trim off disfigured leaves and infested flowers. Bag the cuttings at once, since adults fly off them.

Rinsing works best when you repeat it. Each shower removes larvae that hatched since the last one, before they grow up and lay eggs. Meanwhile, a plant you cannot carry to a shower can be wiped leaf by leaf with a damp cloth.

2. Refresh the potting mix

Because most pupae sit in the top of the soil, swapping it out removes a whole generation. Scrape off the top layer of mix and replace it, or repot into fresh mix. The University of Maryland also advises against potting mixes high in organic matter. Keep in mind that this does nothing for the insects on the leaves.

3. Raise the humidity

Dry indoor air suits thrips. The University of Maryland says high humidity may discourage them, and the Missouri Botanical Garden suggests keeping plants moist and raising the humidity. A humidifier or a tray of wet pebbles helps, though on its own it will not clear an infestation.

4. Insecticidal soap or horticultural oil

Soap and oil are the gentlest sprays, and they kill on contact. The catch is that they only work while wet. The University of Maryland’s experts explain that dried residue does nothing and some stages are protected, so several applications are needed. Use one or the other, not both, and check the label for the wait between sprays.

Cover every surface, especially leaf undersides, leaf joints and new growth. Test a few leaves first, since some plants are sensitive. Neem oil works the same way, and UC IPM lists neem, soap and narrow-range oil among the contact products. Always use a product made for plants, not dish soap.

5. Spinosad

Spinosad is the strongest of the low-toxicity options. UC IPM says it is generally more effective against thrips than soaps and oils, and it lasts a week or more. UF/IFAS lab work found it effective against the new pepper thrips too. It soaks into the leaf, so it keeps working after it dries.

It does not travel to leaves that grow later, so the Maryland experts advise spraying new growth as it appears. Outdoors, keep it off open flowers: UC IPM says it is toxic to bees and natural enemies for about a day after spraying. Use only a spinosad product labeled for houseplants or the plant you are treating.

6. Predatory mites and other natural enemies

Predatory mites are a real option for a large collection or a plant cabinet. However, each one eats only certain stages. UConn Extension says Neoseiulus cucumeris and Amblyseius swirskii feed only on young first-stage larvae, while minute pirate bugs (Orius) eat all stages. Soil-dwelling mites and rove beetles eat the pupae in the mix.

No predatory mite eats the adults, as Reddit growers point out, so release them early and keep releasing. The University of Maryland warns that bought predators may not suit dry indoor air and that enclosed spaces need repeat releases. It also advises never releasing lab-raised predators outdoors, so use them inside only.

Beneficial nematodes, Steinernema feltiae, are a soil drench for the pupae. The University of Maryland lists them, along with fungi such as Beauveria bassiana. Outdoors, minute pirate bugs hunt thrips all summer; our guide to small black bugs explains why the same bug sometimes nips people in late summer.

7. Systemic insecticides, last and with care

Systemic granules are the most recommended fix on houseplant forums. The evidence is weaker than the hype. UC IPM says imidacloprid, the ingredient in most houseplant granules, commonly fails to give satisfactory thrips control and is generally not recommended. The University of Maryland treats it as a last resort and notes that resistance is possible.

If you still choose one, know what to expect. The Maryland experts say granules take several days to over a week to start working and can last a couple of months. Systemics do not touch eggs or pupae, because those do not feed. Never use them on a plant that will flower outdoors where bees visit, or on edible plants unless the label allows it.

Which treatment reaches which stage

This is why one method alone fails. Each treatment reaches only some stages, and the eggs inside the leaf are protected from nearly everything. The table sums up how each method works, so you can see the gaps a single step leaves.

Our summary, built from how each method works as described by UC IPM, the University of Maryland Extension and UConn Extension. “Not shown” means we found no source either way.

How long it takes to get rid of thrips

Plan on about 6 weeks. At normal room temperature, the egg-to-adult cycle takes roughly 2 to 4 weeks, going by the University of Maryland’s figures. Eggs that were already in the leaves on day one keep hatching for a week or two. You need to keep killing the young until every one of those eggs has hatched, and then a little longer.

Our timeline, built from the life cycle figures in the University of Maryland Extension, the Missouri Botanical Garden and NC State Extension. Warmer rooms run faster, cooler rooms slower.

Most people stop after one or two sprays, when the plant looks clean. That is exactly when the hidden eggs hatch. Keep going for the full six weeks, even when you see nothing, and the cycle breaks for good.

What does not work, or is not proven

Some of the most shared thrips fixes online are risky or have nothing behind them. The worst offenders are homemade sprays and garden insecticides used on houseplants. Here is what the evidence says, so you can skip straight to what works.

• Myth 1

  “Dish soap and water works as well as insecticidal soap.”

  Truth: Household soap and detergent are not the same product. The University of Maryland says not to use household soap or detergent, or to mix your own sprays. Dish soap is not a registered pesticide.

• Myth 2

  “A homemade rubbing alcohol spray gets 100% of them.”

  Truth: Alcohol is not a registered pesticide, and rubbing alcohol can catch fire. EPA warns that it can ignite with a spark. Use a labeled insecticidal soap or spinosad instead.

• Myth 3

  “Sevin will clear houseplants for months.”

  Truth: Sevin is carbaryl. UC IPM says to avoid carbaryl for thrips: it is not particularly effective on most thrips, it kills natural enemies and bees, and it can trigger spider mite outbreaks. Never use a product indoors unless the label allows it.

• Myth 4

  “One dose of systemic granules ends it.”

  Truth: UC IPM says imidacloprid commonly fails against thrips, and resistance is possible. Granules also miss eggs and pupae, which do not feed.

• Myth 5

  “Diatomaceous earth around the plants will catch them as they drop.”

  Truth: Diatomaceous earth should only be used as an EPA-registered product, applied as the label directs, not spread across floors and shelves. Fresh potting mix or soil predators deal with the pupae more reliably.

• Myth 6

  “Hydrogen peroxide or vinegar will kill them.”

  Truth: We found no extension testing of either against thrips, and neither is registered for it. Stick with treatments that have evidence behind them.

• Myth 7

  “Sticky traps alone will solve it.”

  Truth: Traps catch only adults that fly. Larvae and eggs stay on the plant, so traps are a scoreboard, not a cure.

• Myth 8

  “You have to throw out the whole collection.”

  Truth: Rarely. Isolate, treat every plant that shows signs, and judge each one by its new growth. Only virus-infected or hopeless plants need to go.

How to prevent thrips

The best prevention is keeping new plants apart for 2 to 3 weeks, as the Missouri Botanical Garden advises, and checking them with a white paper shake before they join the others. Add a sticky card near your plant shelf so you catch the first adults early. Most outbreaks start with one new plant.

• Quarantine every new plant for 2 to 3 weeks, in another room.
• Check plants before they come in for fall. Shake them over white paper and rinse them first.
• Keep cut flowers away from houseplants. Many kinds live in flowers, so a vase from the garden can carry them in.
• Raise the humidity in dry winter months.
• Go easy on nitrogen fertiliser. UC IPM and the University of Maryland both say excess nitrogen can increase numbers.
• Check new growth weekly, since that is where they feed first.

Thrips outdoors: roses, flowers and vegetables

Outdoors, thrips are a normal part of the garden and often need no action. Native predators such as lacewings, minute pirate bugs and predatory mites keep them in check. Act when you see damaged flowers on roses, scarred peppers, or a virus in tomatoes, not just because a few are present.

The University of Maryland advises planting a mix of flowers to feed natural enemies, avoiding excess nitrogen, removing weeds that host them, and spraying the young off with water. On roses, cut off and bin infested buds and spent flowers. On vegetables, pull plants with signs of a virus. Also, UC IPM notes that pesticides cannot repair injured tissue, so control often shows only in next season’s growth.

If you do spray outdoors, protect the pollinators. Use soap, oil or spinosad, and keep spinosad off open flowers. UC IPM advises against broad-spectrum products such as acephate, malathion, carbaryl, bifenthrin and permethrin, which kill the natural enemies and can set off spider mites. For a broader garden pest routine, see how to get rid of aphids, which uses the same soap and water approach.

When to call someone

Most thrips problems are a do-it-yourself job. Still, call your county extension office if vegetables or flowers show signs of a virus. The same goes for a valuable collection that keeps getting reinfested after six weeks of treatment, or an insect you cannot name. They can identify the species and suggest a plan for your area.

• Your county extension office for an ID, a suspected plant virus, or a crop problem.
• A licensed pest professional or arborist for large trees or hedges, or when a systemic or tree treatment is being considered.
• The garden center or nursery where you bought a plant that arrived infested.
• A doctor only for a bite with the warning signs listed above.

Not sure it is thrips at all? A clear close-up of the insect through our bug identifier by picture will tell you before you spend money on the wrong treatment.

Pest control disclaimer. Photo-based identification can help, but it is not always perfect. For dangerous spiders, large infestations, or anything you are unsure about, contact a licensed pest control professional.